Explosive flask for illuminating detonation phenomena



Sept. 25, 1956 G. H. MEssERLY HAL 2,764,094

EXPLOSIVE FLASK FOR ILLUMINATING DETONATION PHENOMENA original Filed Nov 7, 194e Eem" E' ME5EE1-13 and Hr'ur' W."Eam}lhall ewfmfm/w George H. Messerly, Lock Haven, Pa., and Arthur W. Campbell, Los Alamos, N. Mex., assignors to the United States of America as represented by the Secretary of the Army Original application November 7, 1946, Serial Nos.

708,390. Divided and this application October 25, 1951, Serial No. 253,064'

3 Claims. (Cl. 102-87) In: our application Serial Number 708,390, filedV November 7, 1946, now Patent 2,653,073, dated September 22, 1953, of. which they present application is a division, we havedisclosed a. method of and apparatus', for' photographing detonation phenomena of explosive charges by the light of the flash produced by a second charge of explosive detonated in timed relation with the charge under investigation. One of the component parts of the apparatus disclosed and claimed in the aforesaid parent application is a ask for mounting the second or illuminating charge within a body of gas having positive shock wave properties and for positioning the illuminating charge in desired or optimum position with respect to the charge whose properties are under investigation.

It is therefore, the principal object of our invention to provide a flask or container of the aforesaid type which may be easily and quickly assembled about an illuminating explosive charge to hold the charge in symmetrically spaced relation with the walls of the ask, to facilitate the filling of the space between the charge and walls of the ask with a gas having positive shock wave properties, and to maintain the gas undiluted until the ask is used.

Other objects and advantages of the invention will be apparent from a study of the following description in connection with the accompanying drawing wherein the single figure shows a central axial cross section through the completed ask.

Referring in detail to the drawing the charge 1 is shown as two hemispherical halves 2 and 3 fitting together along a normally vertical plane 18 perpendicular to the plane of the ligure. Each half has a semicylindrical radial groove which, when the halves are in mating relation, form a cylindrical channel or bore 5 extending nearly to the center of the spherical charge.

The flask 8 is formed of a transparent or translucent substance such as glass, and is divided into an upper portion 9 having a neck l2, and a lower hemispherical portion 10. As shown, the two portions are separable in an equatorial plane 19 normal to plane 18 and the plane of the figure. The two halves 9 and 10 are united by any suitable means such as collodion or a length of Scotch tape 15. If desired, gasket compound or other suitable sealing material 20 may be used between the meeting surfaces to effect a gas-tight joint.

As shown, the radius of the spherical charge 1 is materially less than the inside radius of the flask and spacers 11 of suitable material such as cork, having a thickness equal to the difference of the two radii, are regularly positioned between the charge and llask to maintain the two in lixed relation. The space 8a thus formed is adapted to be lled with a gas, such as argon, having'positive luminous shock wave properties. Split plugs 13 and 14 are positioned within the neck 12 and collectively dene a passageway by which a length of fuze cord 6, such as primacord, is led from the ask. As shown, this fuze cord has a portion of its length within the tlask wrapped with a length of metallic foil 7, such as lead,

United States Patent() ice to. form a cylinder substantially equal in diametento that of bore 5. The cylindrical wrappingmay conven.. iently extend? through plug 13. It'will benoted thati'the.; wrapping, 7 andv` the fuze cord terminate. within charge. 1 closely adjacent; the center thereof. Bye this. construe:- tion' it is assuredI that the charge 1', is initiateld at the; center thereof.

In assembly.,d spacersv 11A may be; secured by adhesive; in proper positions within sections 9 and 10'; Thereafter the fuze cord 6, its foil wrapping.` 7, and plugs; 13. and 14V arevpositioned withinA neck 12. andther charge 1' with its twoy halves 2- and 3,: inassembled. relatiom, are; positioned as shown. The lower hemispherical. aslr portion 10 is then; placed. in position and the two portions. aref secured together by tape 15.V The entire.v flask. is` lthen placed withina desiccator, with opening; 1U un covered, and after. exhaustion ofthe air therein,- argon; gas isadmitted. toy tllthespace; between the; flask mdfy charge at atmospheric pressure. The opening 17 is then sealed with a drop of collodon. In order to mimimize leakage of gas, the ask may be left within the desiccator, filled with argon until ready for use.

In a flash bulb successfully and extensively used for the described purpose, the charge consisted of 200 grams of a sphere of cast pentolite 21/2 in diameter. The ilask was of approximately 200 cc. capacity, and a space of about 376 radial dimension was provided between the charge and ask. The end of the fuze cord terminated about 1A above the center of the spherical charge. Lead foil 1/32 in thickness was used to wrap the end of the fuze cord. By this construction the detonation wave from the centrally-initiated spherical charge produces simultaneously all over the charge surface an intensely luminous shock wave in the argon surrounding the charge. The approximate duration of the light is the time required for the blast wave to travel the distance between the surface of the charge and the wall of the flask. This time, in the flask described, is about 0.8 microsecond and gives a photographic intensity of the order of l03 candlepower. The duration time of the flash can therefore be varied by varying the radial spacing between the charge and flask. Any asymmetry in the detonation wave will also increase the duration time. However, this is undesirable not be determined or controlled and if excessive will produce blurring and indistinctness of detail in the resulting photograph. It is therefore rather important that the end of the fuze cord be carefully located just above the center of the charge, and that the fuze cordv be shielded as shown to insure initiation of the charge occurring only at the end of the cord within the charge, that is, at substantially the center of the charge.

By the invention just disclosed, an illuminating ask may be readily prepared. The flask is relatively inexpensive and easy to position in proper relation with the explosive charge to be photographed.

Having now fully disclosed the invention, what we claim and desire to secure by Letters Patent is:

1. A flash bulb comprising a generally spherical thinwalled llask of transparent shatterable material having an integral tubular neck portion extending therefrom along a radius of said ask, said flask being divided into two parts on an equatorial plane normal to said radius, a solid, unencased spherical detonating explosive charge within and of lesser diameter than said flask, spacers positioned between said tlask and charge to hold the latter centralized within said ilask, detonating fuze cord means having one end anchored within a radial bore in said explosive charge and extending from substantially the center of said charge through said neck portion to the exterior of said ask, shielding means of metallic foil within said neck portion and extending about said fuse since the duration time can- 1 charge Withnsaid container l the diameter of said container, Arneansmounting said l charg'ein concentric relation with said container to form jtorial plane normal to cord means, a body of gas having positive luminous shock Wave propertiestllingithc. space between saidexplosive- `'charge land llask,l andr sealing means ,parts together in gastightrelation. l f

l 2; A' lflash bulb forproducing a 1 of short duration,

securing lsaid lfizfisk comprising a 'closed transparent` generally spherical container n of materiaL: Ya spherical unencased detonating explosive having a diameter lessthan high inter'lsityl `flash y hernispheres in a plane containing the axis of said neck,A l

` j passage ywhen saidhems-pheres are in assembled mating relation, spacers betweenl said charge land ask holding rsaid charge in concentricl frangble llight-wrmeable l f l 'lengthof explosive a space of uniform radial dimension between said charge and container and shielded fuse` meansr fory initiating said charge at the center thereof, said fuse means comprisr ing a length of detonating stantiaily the center-osaid charge tothe rexterior of said.

container. f f

said A:flask being divided into two portions in anl equafuse cord extending from subf n :3.1m a iiash bulb ofthe typedescribed, a tralislmrenty l generally :spherical ask having anl integral .tubular neck,`

the axis of said necio,` a sphericall explosive charge in 'said containerand of less diameter portion of said cord than said container, said charge being divided into two there being channels insaid herm'sphejres forming aradial relation withA said flask, a

cord extending lthrough lsaid said cord and neclgrneans uniting the portions of said flask in gas tight relation, rarnetallic shield about that Within said sphere, and argon gas iilling` the space between rsaid charge andask.

`fuse cord having one end extending` into said passage and terminatingl 'at the approximate center of said sphere, said lneck tothe exterior ofsaid flask, sealing means between Clarke et at; ...y gn July 15,1957.;A i 

